Cleaning and Stain Removal - "caulk" on clothes

The maintenance dept. at my kids' school filled in a leaky roof with some kind of white "caulk" type of material. It leaked through the ceiling and onto the floor of the locker room. My daughter stepped in it and got it on her canvas Converse shoes, then put her shoes in the same gym bag as her clothes, spreading it to her jeans and a knit shirt. Now it has dried into a rubbery substance that I guess will be impossible to remove. I've tried De-Solv-It on her shoes and the substance does come off of the soles of the shoes. I've picked some of it off of the canvas part and from her jeans but she will outgrow the clothes before I get it all picked off. Any suggestions would be so appreciated!

Scrape off all excess with a dull knife, preferably disposable plastic knife. If you had success with De-Solv-It, continue to use it on affected areas on fabric, blotting from outside toward middle to prevent spreading. Use white rag or paper towels to prevent imparting dye to fabrics. Repeat applications will likely be required.

I can help if I know what type of caulk it is. Polyurethane, silicone, or latex. Maybe your daughter can find out.